Field of Invention
The present invention relates to a field of artificial material, particularly relates to a photonic crystal supporting high frequency sensitivity self-collimation phenomenon and design method and use thereof.
Description of Related Arts
Photonic crystals are artificial materials for controlling electromagnetic wave propagation, which are characterized with a periodic distribution of refractive index and a dispersion relation of photonic band-gap structure. Photonic crystals have rich and controllable dispersion properties, and can be used to construct various integratable optical elements with micro-scales. The self-collimation phenomenon of photonic crystals [H. Kosaka et al., Phys. Rev. B 74,1912 (1999); J. Witzens et al., IEEE Journal of Selected Topics in Quantum Electronics, 8, 1246(2002)] is a special dispersion relation inside a band of the photonic crystals, which ensures that a light beam of finite width maintains collimated during the propagation in a photonic crystal without boundary limits or participation of nonlinear effect. With regard to a two dimensional photonic crystal and a photonic crystal slab, the self-collimation phenomenon originates in straight equi-frequency contours; while with regard to a three dimensional photonic crystal, the self-collimation phenomenon originates in flat equi-frequency surfaces. It has been revealed in prior literatures that, the self-collimation phenomenon of photonic crystals can be used as a flexible waveguiding mechanism with very strong anti-crosstalk capability [X. Yu and S. Fan, Appl. Phys. Lett. 83, 3251 (2003); P. T. Rakich et al., Nature Materials 5, 93 (2006)]. Further, it also has been revealed in literatures that, the self-collimation phenomenon of photonic crystals can be used to design various integratable optical elements, such as interferometer [D. Zhao et al., Appl. Phys. Lett. 90, 231114 (2007)], filter [X. Chen et al, Optics Express, 17, 19808(2009)] and beam splitter [V. Zabelin et al., Optics Letters, 530 (2007)] and the like.
A strict establishment for the self-collimation phenomenon requires that the curvature of the equi-frequency contours (or equi-frequency surfaces) is zero, which is satisfied only at some specific frequencies, while those specific frequencies are named as self-collimation frequency, and midpoints of the equi-frequency contours (or equi-frequency surfaces) with curvature being equal to zero are named as self-collimation point. Normally, self-collimation phenomenon is approximately established within a certain frequency range with curvature of the equi-frequency contours being close to zero around a self-collimation frequency. The width of the frequency range depends on the change rate of curvatures of the equi-frequency contours over the frequency around the self-collimation frequency. The change rate of curvatures of the equi-frequency contours over the frequency around the self-collimation frequency may also be named as self-collimation frequency sensitivity, since it describes the sensitivity of self-collimation phenomenon to frequency change. Currently, the disclosed literatures on the optimizing of self-collimation phenomenon are mostly to decrease the self-collimation frequency sensitivity, such that the self-collimation phenomenon is approximately established within a wider frequency range [R. E. Hamam et al., Optics Express, 17, 8109-8118 (2009); Y-C Chuang, T. J. Suleski, J. Opt., 12, 035102(2010)].
It should be pointed out that, it is of significant importance to improve the self-collimation frequency sensitivity. For example, according to the disclosed information in the literature [X. Jiang et al., Appl. Phys. Lett., 91, 031105(2007); Z. Xu et al., Optics Letters, 33, 1762 (2008)], around the self-collimation frequency, variations of refractive index caused by optical nonlinearities will make degree of diffraction change among positive, zero, and negative value, while the change of degree of diffraction will in turn affect the intensity of optical nonlinearities, thereby forming novel physical phenomena such as optical solution, self-locking effect of beam width and the like; the improvement of self-collimation frequency sensitivity can help to enhance the interaction between diffraction and optical nonlinearities around the self-collimation frequency, thereby significantly decreasing the required lowest energy intensity for those physical phenomenon. Moreover, it can be predicted that, the improvement of self-collimation frequency sensitivity also can help to improve the performance of a number of existing photonic crystal devices based on self-collimation phenomenon, and to make new designs of novel photonic crystal devices become feasible.
Therefore, it becomes an urgent technical issue for those skilled in the art that how to provide a photonic crystal supporting high frequency sensitivity self-collimation phenomenon and design method and use thereof.